The invention concerns a method for thermally regenerating the heat exchanger material of a regenerative post-combustion device, which in a housing includes from top to bottom:
a) a combustion chamber;
b) a section, which is divided into several segments filled with heat exchanger material,
c) a rotary distributor, which according to its rotary position produces:
ca) a connection between an inlet connection for exhaust gas to be purified with a first segment of the heat exchanger material;
cb) a connection between a second segment of the heat exchanger material and an outlet connection for purified gas;
cc) a connection between a third segment of the heat exchanger material, leading the second segment in the rotational direction of the rotary distributor, and a connection for flushing gas,
in which method fresh air is heated in the combustion chamber and is fed one after another through all the segments of the heat exchanger material, as a result of which the heat exchanger material is brought to a temperature, at which the contaminants absorbed in the heat exchanger material are released.
Regenerative post-combustion devices serve to purify contaminated exhaust gases from industrial processes. To conserve energy during the thermal post-combustion the exhaust gases to be purified are fed through heat exchanger material. Since the exhaust gases to be purified frequently contain organic contaminants in the form of condensable substances, for example tar products or organic dusts, the surfaces of these heat exchanger materials clog up during the course of operation with these contaminants. To regenerate the heat exchanger materials these must be periodically heated to a temperature at which the contaminants absorbed on the surface are released and can be carried away. This happens with the known thermal post-combustion devices due to the fact that fresh air is introduced into the combustion chamber, heated there to high temperature and then fed from the top through the heat exchanger material to the bottom, taken via the rotary distributor to the outlet and then evacuated to the outside atmosphere via the flue. The rotary distributor stops during this process. There is a wait until the segment of the heat exchanger material flushed through in each case from top to bottom has heated up to the necessary temperature, so that any contaminants are released from all areas of the heat exchanger material in this segment. Afterwards the rotary distributor is advanced by one segment and the process begins again from the start.
The disadvantage with this known method to regenerate the heat exchanger material is on the one hand the relatively long time which is required to clean all the segments. Furthermore the gas ducted to the flue contains contaminants, which have been released from the heat exchanger material, and therefore is not clean.
Aim of the present invention is to create a method of the type mentioned at the beginning in such a way that no contaminants are emitted into the surrounding atmosphere.
This aim is achieved according to the invention by the fact that the air heated in the combustion chamber for thermal regeneration is fed from the combustion chamber via a segment of the heat exchanger material downwards and via the rotary distributor to the inlet or outlet connection and from there is once again fed directly into the combustion chamber and that the air is ducted in the circuit with the rotary distributor stopped until the heat exchanger material in the segment is sufficiently hot and all contaminants are released from this, whereupon this process is carried out in turn for all the other segments.
Because in the case of the method according to the invention the hot air escaping from the heat exchanger material is not fed directly to the flue but is fed again into the combustion chamber of the post-combustion device for further post-combustion, the hot gases used for regeneration also leave the post-combustion device completely clean; contaminants are not emitted into the outer atmosphere via the waste gas flue.
Many known post-combustion devices are designed so that either the inlet or the outlet is not connected directly via a pipe with the rotary distributor. Rather the inlet or the outlet first leads into a plenum chamber in the lower section of the housing of the post-combustion device which then in its turn communicates with one of the different channels of the rotary distributor. The other particular connection communicates via a pipe with the rotary distributor. Should with the method according to the invention post-combustion devices of this design be thermally regenerated, it is recommended that the air used for regeneration is fed via that connection which does not communicate with the plenum chamber. This has the advantage that the number of components of the post-combustion device which come into contact with the hot air and therefore must resist high temperature, can be kept relatively small. Additionally in this way the connecting pipe between the connection and the rotary distributor can be cleaned, which is especially important if the connection in question concerns the inlet connection.
The oxygen needed for oxidation is supplied by fresh air.